An ESD event refers to a phenomenon of electrical discharge of a current (positive or negative) for a short duration during which a large amount of current is provided to an integrated circuit (IC). The large current may be built-up from a variety of sources, such as the human body. An ESD event commonly results from the discharge of a high voltage potential (typically, several kilovolts) and leads to pulses of high current (several amperes) of a short duration (typically, 1 nanosecond to 1000 nanoseconds). An ESD event is generated within an IC, illustratively, by human contact with the leads of the IC or by electrically charged machinery being discharged in other leads of an IC. During installation of integrated circuits into products, these electrostatic discharges may destroy the IC and thus require expensive repairs on the products, which could have been avoided by providing a mechanism for dissipation of the electrostatic discharge to which the IC may have been subjected.
Manufacturers and users of ICs must take precautions to avoid ESD. For example, ESD prevention can be part of the device itself and may include special design techniques for device input and output pins. Additionally, external protection components can also be used with circuit layout. For example, to protect ICs from an ESD event, many schemes have been implemented, including use of a silicon controlled rectifier (SCR). An SCR can sustain high currents, hold the voltage across the SCR at a low level and may be implemented to bypass high current discharges associated with an ESD event.
Thus, an SCR device may be the proper ESD solution for high speed differential inputs and outputs (IOs). For example, an SCR typically provides less capacitive loading as compared to a diode. Additionally, an SCR provides better ESD protection as compared to a string diode.
However, size constraints may also be an issue when using SCRs for high-speed differential IOs. For example, two separate diode-triggered SCRs on differential pads take up a large area on the device. In contrast, a compact SCR make take forty percent less area than two separate SCRs.
Accordingly, there exists a need in the art to overcome the deficiencies and limitations described hereinabove.